Explain the Anti-Diuretic Hormone (ADH)

It is secreted by the pituitary gland and controls the ability of water to pass through the cells in the walls of the collecting ducts. If ADH is not present, then water cannot pass through the walls of the ducts. The more the ADH present, the more water can pass through. Just now we have studied about the specialized nerve cells called as osmoreceptors that are present in the hypothalamus of the brain. These cells, as you would recall, sense the Na concentration of the blood.

The nerve endings of these types of osmoreceptors are situated in the posterior pituitary gland and secrete ADH. Whether the Na concentration of the blood is high, the osmoreceptors secrete ADH. If the Na concentration of the blood is low, they do not secrete ADH. Actually, there is all time some very low level of ADH secreted from the osmoreceptors. Thus we can see that the electrolyte balance is always maintained by the kidneys.